Electrical switch with contact grounding strap



W. N. SCHINK Sept. 6, 1966 ELECTRICAL SWITCH WITH CONTACT GROUNDING STRAP Filed Nov. 8, 1965 United States Patent O 3,271,536 ELECTRICAL SWITCH WITH CONTACT GROUNDING STRAP William N. Schink, Crystal Lake, Ill., assignor to Indak Manufacturing Corp., Northbrook, Ill.., a corporation of Illinois Filed Nov. 8, 1965, Ser. No. 506,699 9 Claims. (Cl. 200-16) This invention relates to electrical switches.

One object of the present invention is to provide a new and improved electrical switch having a strap securely connected between one of the contacts and the casing for grounding the contact to the casing.

A further object is to provide a new and improved switch of the foregoing character in which the grounding strap is firmly secured between a rivet connected to the contact and a tab projecting from the casing.

Another object is to provide a new and improved switch of the foregoing character in Which'the grounding strap is mounted on an insulating terminal board and is eifective not only to ground one of the contacts, but also to secure the terminal board to the casing of the switch.

A further object is to provide such a new and improved switch in which the tab on the casing extends through a slot in the ground strap and is securely staked to the strap.

Another object is to provide such a new and improved switch in which the ground strap is securely clamped against a shoulder on the tab.

A further object is to provide a new and improved electrical switch in which the grounding of one of the contacts is accomplished at extremely low cost.

Further objects and advantages of the present invention will appear from the following description, taken with the accompanying drawings, in which:

FIG. 1 is a rear elevational view of a switch to be described as an illustrative embodiment of the present invention.

FIG. 2 is a side elevational view of the switch.

FIG. 3 is an enlarged fragmentary elevational View, partly in longitudinal section.

FIG. 4 is a rear elevational view with the terminal board removed, taken generally as indicated by the line 44 in FIG. 3.

FIG. Sis a sectional view showing the front or inner side of the terminal board, the view being taken along the line 5-5 in FIG. 3.

FIG. 6 is a fragmentary enlarged section, taken generally along the line 66 in FIG. 5.

FIG. 7 is a rear elevational view of a modified switc'h constituting another embodiment of the present invention.

It will be seen that FIGS. 1-5 illustrate an electrical switch 10 which is of a type particularly well adapted for automotive services. However, it will be understood that the present invention is applicable to switches of various types.

The illustrated switch 10 comprises a casing 12 which is made of metal and thus is electrically conductive. A contactor 14 is movably mounted within the casing 12. The contactor 14 is carried by a slider or carriage 16, preferably made of plastic or other insulating material.

To move the carriage '16, the switch 10 is provided with an operating lever 18 which is pivoted on a bracket 20 secured to the front wall 22 of the casing 12. In FIGS. 1-5, the invention is illustrated in connection with a lever-action switch, but it will be understood that the invention is applicable to other types of switches. The operating lever 18 has an arm 24 which projects rearwardly through a slot 26 in the front wall 22. The arm 24 is received in a slot or opening 28 formed in the carriage 16.

The switch 10 is provided with a plurality of contacts which are adapted to be engaged by the contactor 14. The number of contacts and the arrangement thereof may be varied, but the illustrated switch has four contacts 30, 31, 32 and 33. Preferably, the contacts 30-33 are mounted on an insulating terminal board or plate 34 which is secured to the casing 12 so as to form a rear wall thereof. The illustrated contacts 30-33 are in the form of rounded heads formed on the front ends of rivets 40-43 which extend through the terminal board 34. In the case of the rivets 40, 42 and 43, terminals in the form of prongs or lugs 50, 52 and 53 are securely connected to the rear ends of the rivets. In accordance with the present invention, a grounding strap or plate 51 is securely connected to the rear end of the rivet 41. A hole 54 is formed in the grounding strap 51 to receive the rivet 41.

As shown to best advantage in FIGS. 1 and 3, the grounding strap 51 is in the form of a metal plate which is mounted against the rear side of the insulating board 34. In addition to being secured to the rivet 41, the grounding strap 51 is secured to the casing 12, so that the contact 31 will be grounded to the casing. Preferably, the grounding strap 51 is formed with a slot or opening 56 to receive a tab or lug 58 which projects rearwardly from one side wall 60 of the casing 12. It will be seen that the lug 58 is formed with rearwardly facing shoulders 61 for engaging the grounding strap 51. The rear portion of the lug 58 is securely anchored to the ground ing strap 51. Thus, as illustrated to best advantage in FIGS. 1 and 6, the lug 58 has portions 62 which are staked or upset so as to overlap the rear side of the grounding strap 51. The staked portions 62 are effective to clamp the grounding strap 58 very securely against the shoulders 61. In this way, the grounding strap 51 is securely fastened to the casing 12, as well as being electrically connected thereto. If desired, the lug 58 may be formed with a rib 63 which stiffens the lug so as to insure that it will not bend or crumple during the staking operation. The stiffening rib 63 extends longitudinally along the shouldered portion of the lug and also along the adjacent portion of the casing 12. The grounding strap 51 also holds one side of the insulating board 34 against the casing 12. It will be seen that the tab 58 extends through a slot 64 formed in one edge of the insulating board 34.

As shown, the insulating board 34 is secured to the casing 12 at two other points by means of additional tabs 66 and 68 on the casing 12. These tabs extend through slots 70 and 72 in the insulating board 34 and are bent inwardly behind the insulating board.

The contactor 14 is pressed rearwardly by means of a spring 74 which is interposed between the contactor and the carriage 16. The illustrated spring is of the coiled compression type, but other types of springs may be employed. In addition to biasing the contactor rearwardly, the spring 74 biases the carriage 16 forwardly.

To locate and detain the carriage 16 in its various positions, the front wall 26 of the casing 12 is formed with alternate detent projections 76 and notches 78'. Detent projections 80 are formed on the carriage 16 to ride over the detent projections 76 and into the notches 78. The spring 74 provides retaining force between the detent projections 80 on the carriage 16 and the detent elements 76 and 78 on the casing 12.

In this case, the contactor 14 and the operating lever 18 are movable to four positions which are designated OFF, LOW, MEDIUM and HIGH. In the OFF position, the contactor 14 engages only the contact 30. In the LOW position, the contacts 30 and 31 are engaged by the contactor. In the MEDIUM position, the contactor 3 engages the contacts 30, 31 and 32. In the HIGH position, the contactor 14 engages the contacts 31, 32 and 33. It will be understood that the invention is applicable to switches having other contact arrangements.

As already indicated, the contact 31 is grounded to the casing by the grounding strap or plate 51. Inasmuch as the contactor 14 engages the contact 31 in the LOW, MEDIUM and HIGH positions, the contactor is grounded to these positions. Thus, in the successive positions, the contactor 14 forms connections to ground from the contacts 30, 32 and 33.

The illustrated switch is well adapted for use in circuits which call for the grounding of the contactor. 'A motor speed control circuit 82 of this type is illustrated by way of example in FIG. 1. The circuit is energized by a battery 84 having one side grounded. The casing 12 of the switch is also grounded. A motor 86 is connected between the ungrounded side of the battery 84 and the terminal 43. A current limiting resistor 8-8 is connected between the terminals 52 and 53. Another resistor 90 is connected between the terminals 50 and 53.

When the contactor 14 engages the contacts 30 and 31, both of the resistors 88 and 90 are in series with the motor 86, so that the motor is operated at low speed. When the contactor 14 engages the contacts 30, 31 and 32, only the resistor 88 is in series with the motor, so that it operates at medium speed. When the contactor 14 engages the contacts 31, 32 and 33, both of the resistors 88 and 90 are out of circuit so that the motor 86 operates at high speed.

The grounding strap 51 forms a ground connection between the contact 31 and the casing 12 at extremely low cost, At the same time, the grounding strap and the staked tab 58 form a secure mechanical connection to hold the insulating terminal board 34 against the casing.

' terminal board 94 carries a plurality of contacts 98-, 99

and 100 which include rivets 102, 103 and 104. Terminal lugs or prongs 106 and 107 are mounted on the rivets 103 and 104. However, a grounding strap or plate 108 is secured to the rivet 102 and is mounted against the rear side of the insulating terminal board 92.

To secure the terminal board 94 to the casing 96, rearwardly projecting tabs 110 are formed on the casing. The tabs 110 extend through notches or slots 112 in the terminal board 94 and are bent over or folded behind the terminal board.

The illustrated grounding strap 108 is securely connected to the casing 96 by means of a shouldered tab or lug 114 which is essentially the same as the lug 58 of FIGS. 16. As before, the grounding strap 108 is slotted to receive the reduced rear end portion of the lug 114. The rear end of the lug 114 is securely staked or upset against the rear side of the grounding strap 108 so as to clamp the strap against the shouldered portion of the lug.

In each of the illustrated embodiments, a secure elec trical connection between the grounding strap and the casing is assured by the construction whereby the grounding strap is clamped between the staked portion and the I and equivalents may be employed without departing from the true spirit and scope of the invention, as exemplified in the foregoing description and defined in the following ROBERT K. SCHAEFER, Primary Examiner.

claims.

I claim:

1. An electrical switch,

comprising the combination of a metal casing,

an insulating board mounted on said casing,

a plurality of contacts in said casing and mounted on said insulating board,

a contactor movable in said casing into engagement with said contacts,

a metal strap mounted on said insulating board and connected to one of said contacts,

said strap having a slot therein,

and a tab projecting from said casing and through said slot,

said tab having an upset end portion for securing said strap to said tab to ground said one contact to said casing.

2. An electrical switch according to claim 1,

in which said upset end portion comprises staked portions of said tab overlapping said strap.

3. An electrical switch according to claim 1,

in which said tab comprises a shouldered portion engaging said strap,

said strap being clamped between said shouldered portion and said upset end portion.

4. An electrical switch according to claim 1,

in which said strap is mounted on the opposite side of said insulating board from said casing and is effective to secure said insulating board to said casing.

5. An electrical switch according to claim 1,

in which said one contact comprises a rivet extending through said insulating board,

said strap being secured to said rivet.

6. An electrical switch according to claim 1,

in which said tab comprises a shouldered portion engaging said strap,

said upset end portion of said tab comprising staked portions overlapping the opposite side of said strap,

said strap being clamped between said shouldered portion and said staked portions.

7. An electrical switch,

comprising the combination of a metal casing,

an insulating board mounted on one side of said casing,

a plurality of contacts in said casing and mounted on said insulating board,

a contactor movable in said casing into engagement with said contacts,

va metal grounding strap mounted on said insulating board and connected to one of said contacts,

said strap having a slot therein,

and a tab projecting from said casing,

said insulating board having a slot therein for receiving said tab,

, said tab having a shouldered portion received in said slot in said board, said shouldered portion engaging the inner side of said grounding strap,

said tab having a reduced portion extending through said slot in said grounding strap,

said tab having staked end portions overlapping the outer side of said strap and clamping said strap against said shouldered portion of said tab,

said strap being mounted on the outer side of said insulating board and being efiective to hold said board against said casing.

8. An electrical switch according to claim 7,

in which said one contact comprises a rivet extending through said insulating board,

said strap being secured to said rivet.

9, An electrical switch according to claim 7,

in which said tab is formed with a longitudinal stiffening rib.

No references cited. 

1. AN ELECTRICAL SWITCH, COMPRISING THE COMBINATION OF A METAL CASING, AN INSULATING BOARD MOUNTED ON SAID CASING, A PLURALITY OF CONTACTS IN SAID CASING AND MOUNTED ON SAID INSULATING BOARD, A CONTACTOR MOVABLE IN SAID CASING INTO ENGAGEMENT WITH SAID CONTACTS, A METAL STRAP MOUNTED ON SAID INSULATING BOARD AND CONNECTED TO ONE OF SAID CONTACTS, SAID STRAP HAVING A SLOT THEREIN, 